no 2-3 upshift and need car ASAP tks - Page 4 - PeachParts Mercedes-Benz Forum

DieselBone · #46 11-19-2011, 08:39 PM

My `83 was doing the same thing about 6 years ago. Once in awhile it would shift late into 3rd, normal 4th. Then one day it wouldn't shift into 3rd at all. 1 to 2 was fine, reverse was fine. I figured there was some dirt or something in the valve body that didn't let the shift valves work correctly. I never did fix it, or try to fix it. I installed an `85 transmission, and the `83 transmission is sitting in storeage. My vote is on the valve body, good luck!

richclan · #47 01-27-2012, 11:53 PM

i got some time to diag. this trans a little more.

removed the modulator and found it was a little stuck [plastic pin].
the plastic pin survived and was intact when i reinstalled it.
it also holds vacuum

i installed a banjo bolt in place of the plug next to the modulator.
rigged up a line to a compression gauge and read
25 psi at idle in neutral
50 psi in drive @ 2000 rpm

edit: the manual states modulator pressure 42psi at 31 mph
i'll have to do that test/adjustment tomorrow

i wont be able to tell if it up-shifts until i put things back together.

since its dropped down a little is there anything i should check now?????????
thanks

richclan · #48 01-28-2012, 07:34 PM

im getting at the end of my rope with this

the trans was put together no driveshaft and lowered in back a little. i started it up and revved to 2k rpm and it went through all gears to 60mph.
i thought it was fixed, wrong.

put it all together with driveshaft, trans mounts, and topped up the fluid .
no luck with 2-3 shift

triple checked the linkage

removed the pan and adjusted the WOT screw
http://www.w124performance.com/docs/mb/transmission/trans_WOT_upshift_RPM.pdf

put it all back again same thing

i retested the modulator with vacuum and it now bleeds down slowly to 5.

the only thing i can get from all this is the modulator is sticking/ binding / leaking and i dont know this because i dont have a new one to compare it too.
so i guess it only worked for a minute after removed cleaned and replaced it

WHAT DO YOU GUYS THINK??????
IM GOING CRAZY

because im majorly stumped

richclan · #49 01-30-2012, 12:29 PM

i went and ordered a new modulator and pin in case i broke mine
$35 for both, worth a try i guess

Stretch · #50 01-30-2012, 12:51 PM

Sorry to have missed your other posts - have you checked the condition of the rest of the vacuum tubing up top so to speak <= in the engine bay?

There's a new member who has recently joined from Holland - Govert - who has been posting on BenzWorld for a while. He seems to know a lot about the W123 vacuum system - if I were you I'd drop him a PM and ask if he's got the time to trawl his way through this thread. Put it this way, he's the chap I'd be asking for help.

richclan · #51 01-30-2012, 01:08 PM

thanks army
rest of the vacuum tubing up top looks fine.
if modulator doesn't work i'll PM him for sure

whunter · #52 02-01-2012, 12:59 AM

You need to read vacuum feeding the modulator.
The vacuum control valve feeds vacuum, and bleeds vacuum.
If the line fails to drop to zero at the required time, or holds maximum vacuum all the time, shift issues like yours occur.

FYI: You have e-mail..

.

richclan · #53 02-03-2012, 10:07 PM

oh well i tried a $35 fix but no change
i dont know what to do next : test wise
i've looked through the manuals and it seems the trans needs a rebuild. i just cant see it at 60K miles.

im thinking about buying a cheap used 300d with rot but good engine / trans.

or just rebuild this one. sucks to be broke all the time.

fyi:
roy at peach parts tks the parts were a perfect match.

note: modulator replacement on a 722.315 requires these parts, buy only from phill or they will be wrong [ from dealer they are different]
126.270.2679 mod
126.277.2075 pin [.007 larger dia]

richclan · #54 02-11-2012, 01:54 PM

could a broken spring in the valve body cause this prob.??
i rem. reading somewhere about k-2, k-3 b-2 b-3 springs
or maybe install a superior shift kit?

richclan · #55 04-02-2013, 05:25 PM

i thought i would close this thread out.
i had the trans rebuilt. it was the clutches and bands, they were dry-rotted. and the 4th gear clutch was down to metal. so now all new stuff inside trans. and it runs like new.

Stretch · #56 04-03-2013, 03:52 AM

Well thanks for the update

Skippy · #57 04-03-2013, 05:10 AM

I'm guessing lack of use combined with a little condensation or water intrusion did that transmission in. Cars are meant to be driven, but I may be doing a little of "Do what I say, not what I do" since I've only put 32,000 miles on my 300D since I bought it seven and a half years ago. I've had my bike about 15 months and done about 7400 miles.